Portable personal infusion devices and systems are relatively well-known in the medical arts, for use in delivering or dispensing a prescribed medication to a patient. Many pharmaceutical agents are delivered into the subcutaneous tissue and the most common is insulin. Currently, more than 70,000 patients in the U.S. and 30,000 more patients worldwide use continuous subcutaneous infusion of insulin (CSII) for the treatment of diabetes mellitus. However, other medications that are infused include HIV drugs, drugs to treat pulmonary hypertension, iron chelation drugs, pain medications, and anti-cancer treatments.
Traditionally, low cost infusion devices have used an elastomeric diaphragm, sponge rubber, balloon or gas generator to expel fluid to be infused into a patient over a period of time at a single, relatively constant rate. A drawback to these devices is that they are only filled with fluid once. When the infusion of fluid is complete, the infusion device is disposed of. Thus, the infusion device must be made at an extremely low cost. Another drawback is that the low cost may not allow for the high quality needed to have sufficient flow rate control accuracy for the delivery of dosage sensitive drugs.
To obviate these drawbacks, infusion devices have been designed with more accurate dosage control, but at a significantly higher cost. To compensate for the relatively high cost, the more accurate infusion devices are designed to be refilled and reused.
In one form, refillable infusion devices comprise a relatively compact housing adapted to receive a syringe or reservoir carrying a prescribed medication for administration to the patient through infusion tubing and an associated catheter or infusion set. Such infusion devices are utilized to administer insulin and other medications, with exemplary infusion device constructions being shown and described in U.S. Pat. Nos. 4,562,751; 4,678,408; 4,685,903; 5,080,653 and 5,097,122, which are incorporated by reference herein.
While the sophisticated electronics and robust mechanics of the more expensive refillable infusion devices provide a more reliable and accurate infusion device, the cost of manufacturing may make the refillable infusion device too expensive for some users or medications. On the other hand, the low cost, one-time-use, constant flow rate infusion devices may not have sufficient flow rate accuracy or the adjustments needed to control the dosage for some users.